Kisetsu Morita is a Japanese novelist and light novel author known for creating several popular series in the isekai and fantasy comedy genres. Born on April 10, 1984, in Kobe, Hyogo Prefecture, Morita began his writing career after winning an excellence award at the age of 23 in the fourth MF Bunko J Light Novel Newcomer Awards for his work Venezuela Bitter My Sweet, which led to his professional debut in 2008.

Morita is the original creator of the light novel series I've Been Killing Slimes for 300 Years and Maxed Out My Level. The story, which follows an overworked office worker reincarnated as an immortal witch who spends three centuries leisurely defeating slimes only to become immensely powerful, began serialization on the user-generated novel website Shōsetsuka ni Narō in June 2016. The series was later acquired by SB Creative, which published the first light novel volume under its GA Novel imprint in January 2017, with illustrations by Benio. The franchise has since expanded into a manga adaptation illustrated by Yūsuke Shiba, which began serialization in Square Enix's Gangan Online magazine in June 2017, and an anime television series that first aired in April 2021, with a second season premiering in April 2025.

Another notable original work by Morita is I Was a Bottom-Tier Bureaucrat for 1,500 Years, and the Demon King Made Me a Minister. This series focuses on Beelzebub, a lazy demon clerk who has enjoyed a relaxed existence for fifteen centuries before an unexpected promotion to minister upends her life. The light novel, also illustrated by Benio, began publication in July 2017, and a manga adaptation illustrated by Meishi Murakami ran from January 2019 to August 2020.

Morita has also authored other light novel series, including Food for an Elf and Red Dragon Women Academy, both illustrated by Benio, as well as numerous other titles published under various imprints such as MF Bunko J, GA Bunko, and Famitsu Bunko. His broader bibliography includes works like Your Service Is Only That Good?, The Holy Magic is the Pitch Black Urushihara-san, and Tama Days, demonstrating a prolific output across multiple publishers.

A recurring element in Morita's writing is the incorporation of yuri, or female-female romantic and emotional relationships, which he has expressed a personal fondness for in author afterwords. His stories typically feature lighthearted, comedic tones with low-stakes conflict, often focusing on the daily lives of powerful but reluctant protagonists who seek peaceful existences despite their extraordinary abilities. This approach has been characterized as producing soft content that avoids deep conflict elements or intricate world-building, instead prioritizing accessible and comforting narratives.

Morita holds significance in the light novel industry as a consistently productive creator who successfully transitioned from web novel serialization to traditional publishing and multimedia adaptation. I've Been Killing Slimes for 300 Years and Maxed Out My Level represents his most commercially successful work to date, serving as his first franchise to receive an anime adaptation and achieving international release through English publisher Yen Press. The series has reached twenty-six light novel volumes as of 2025, with ongoing manga and anime continuations, cementing Morita's position as a recognizable name in contemporary isekai comedy.